I put some 285/75r18 Toyo MT's on last week and have since seen a 3.0 - 3.5 mpg loss. I came from 275/70r18 continentals....I knew I was going to see a loss, but I thought more in the range of 1.5-2 mpg's.

I am running the fronts at 65 psi and the rear at 70 psi, Continentals were at 65 psi all the way around.

Has anyone else seen this much of a drop from MT tires? Those of you with Toyos, have you played around with tire pressure and seen better results?

Thanks

 

You didn't mention what you were getting before the tire change, but that is more than a 5% gain in tire size. Your odometer is off by that much now and could account for nearly a 1 mpg difference. A wider, taller and heavier tire is going to kill fuel economy on short distance runs especially. The aggressive mud tire vs. the rather smooth Continental makes a difference as well. I would expect a 2 mpg difference overall and you aren't very far off of that once you figure the odometer difference.

 

I did not think of the odometer aspect. I was getting 18 before, I am now getting 14.5-15mpg driving the same 30 mile highway route everyday. All my mpg's are hand calculated as my LCD screen has always been 1 mpg higher than hand.

 

Get your speedometer/odometer re-calibrated for the tire size change. Your taller tires spin less revs per mile than the smaller ones. I ran in to that with my old silverado - went from 265x70r16's to 285x75-r16's.

 

Make sure you hand calculate you mpg's. I went from stock size and stock tires to an 8inch lift to 37's (52 psi all around) and I dropped 3.5 mpgs max so something isn't right with your calculations